Hitherto, there have been hermetically sealed kneaders that knead a material to be kneaded, such as rubber and plastic, such as a hermetically sealed kneader disclosed in Patent Document 1. The hermetically sealed kneader according to Patent Document 1 is configured in such a manner as to knead a material to be kneaded that is pressed into a kneading chamber by two rotors provided in the kneading chamber, and take out the material to be kneaded in a desired kneaded state to the exterior. In these two rotors, a shaft is rotatably supported by bearings on both sides. An end portion of each rotor on a drive side is an input shaft that protrudes to the exterior. Output shafts of an adjacently disposed driving device and these input shafts are connected to each other through connectors, such as a gear coupling.
In the hermetically sealed kneader according to Patent Document 1, a material to be kneaded, such as rubber and plastic, is input at a predetermined rate together with various additives into a hopper from an input port above. This material to be kneaded is pressed into the kneading chamber in a sealed state by a pushing action of a floating weight. The material to be kneaded thus pressed into the kneading chamber is kneaded by the rotors that rotate in directions different from each other. In other words, a driving force (rotation) of a motor is transmitted through a speed reducer to each of the rotors, and the rotors each rotate in such a manner as to sweep an inner wall of the kneading chamber, while rotating in directions different from each other. Thereby, a resin material (material to be kneaded) pressed into the kneading chamber is kneaded together with various additives, and the material to be kneaded in a desired kneaded state is taken out to the exterior.
Moreover, a blade (kneading blade) is provided on an outer circumferential surface of each rotor, and in the hermetically sealed kneader according to Patent Document 1, these blades have a structure spirally twisted relative to an axial line of the rotor. An action of these twisted blades cause the material to be kneaded, such as rubber and plastic, to be pushed in an axial direction, and cause a material flow that delivers the material to be kneaded along the axial direction to be generated. In addition, the blades are twisted such that flows in directions opposite to each other with respect to the two rotors are generated, and the material to be kneaded is allowed to flow in such a manner as to circulate in the chamber, thereby achieving an effective kneading.
Note that, in the hermetically sealed kneader disclosed in Patent Document 1, in other words, in common hermetically sealed kneaders, the material to be kneaded is delivered along the axial direction by the spirally twisted blades formed on the rotors, a counteraction of which causes a reaction force (thrust load) directed in the axial direction to be generated. Since such a thrust load exerts a large influence on the lifetime of the bearings that support the rotors, accurately measuring a thrust load is required for determining the lifetime of the bearings. Moreover, in a case in which a thrust load fails to be accurately grasped, there may arise problems, such as application of a thrust load greater than or equal to that designed to the bearings, or, on the contrary, use of the bearings having excessive capability. Thus, in a case in which the bearings of a type as described above are employed, providing an element that can accurately measure a load applied to the rotors in a thrust direction is preferable.
For example, Patent Document 2 discloses a method of measuring a load applied to a bearing while a load sensor is provided between a bearing body and a casing.